At this time, most people are trading 2 bolts for one party card. I don’t think a 1-1 trade makes much sense because:
1. It costs so much more to get a party card (even though the cost covers the party itself, the cost is about 4x the cost of a booster pack)
2. Party cards are limited edition. Once the party is over, cards are no longer available. But anybody can buy a booster pack.

It will be very interesting to see what happens in a couple of weeks during MNSSHP. If the same cards are re-used from last year, I don’t think the trade ratio will change. But, if a new card is issued, then the 2012 part cards become much more valuable – there will be no more available so they will be much more rare and only obtainable by trade. Personally I’d expect at least 3 bolts for a party card at that point, but that’s just me. We’ll have to see what the “market” bears.